The OH transmission (original) in my '69 Hurst/Olds delays in shifting from 1st into 2nd and from 2nd into 3rd.
The car "jerks" a little when this occurs.
The delay from 2nd into 3rd is more noticeable. I believe in the past it would shift at about 2500rpm but now shifts at 3200rpm.
The transmission was rebuilt 4 years ago, along with the overall restoration of the car (which included an engine rebuild).
The car's been running great until this trans shifting thing began a few days ago.
Today, I checked the trans fluid level, which was low. I filled it as instructed in the 1969 Olds SM, but the issue persists.
Might there be a problem with the vacuum modulator? Any other suggestions?
Thanks.

 

Vacuum modulator could be the problem as could the vacuum supply to the modulator. Check the hose at the intake and at the modulator first for cracks or obstructions.

 

Also check the hose for signs of trans fluid leakage.

 

Pull the governor and see if the plunger is stuck.

 

Gentlemen, thanks for the prompt replies.
Vacuum supply to the modulator was the culprit.
At a car show the past Saturday another participant noticed my PCV valve/supply hose was loose.
In trying to fix it, one of the vacuum lines beneath the air cleaner base became inadvertently dislodged from a "T" connector.
Reconnecting the line did the trick.
That, and adding ATF fluid as noted above, resulted in smooth/on-time shifting.
Thanks again.